German patent document DE 10 2007 038 376 A1 discusses a charging device for charging a battery. With the aid of the charging device, a charging current may be made available by a power supply line, to which the battery may be coupled. In addition, the described charging device is intended to have the function of determining the battery storage capacity. By determining the battery storage capacity, it should be able to be detected if sufficient operability of the battery is ensured.